Project Summary: The capability to manipulate pancreatic function through peripheral nerve stimulation offers exciting therapeutic potential, but will require a deeper understanding of underlying molecular biology as well as inter-organ signaling and communication. Such processes are difficult to study in vivo because they occur on time-scales of seconds to minutes?far faster than can be measured by conventional assays. The primary goal of this project is to develop real-time in vivo biosensors that can continuously measure the physiological concentrations of glucose, insulin and glucagon in specific areas of the pancreas of freely moving animals. Our biosensors will detect these three biomarkers with high sensitivity (pM~nM), spatial resolution (~10 ?m) and temporal resolution (~1 minute), and thereby offer unprecedented insights into the molecular biology of the pancreas. We will be building upon aptamer biosensor technology previously developed by our group, with which we have already demonstrated the first continuous measurement of small molecule drugs in vivo as well as closed-loop feedback control in live animals. This is a ?platform? technology that can be readily adapted to measure a wide range of biomarkers by swapping the aptamer probes, as we have demonstrated previously. Upon successful development of this real-time biosensor for the pancreas, we will expand the range of targets to 20 other biomarkers, including neuromodulators and cytokines that play important roles in peripheral nerve stimulation. To make these biosensor systems available to other researchers, a startup company (RT Biotech) will refine the prototypes and produce them at low volumes for other groups within the SPARC program within 3 years.